WASHINGTON - A Pentagon planning document being updated to reflect the doctrine of pre-emption declared by President Bush in 2002 envisions the use of nuclear weapons to deter terrorists from using weapons of mass destruction against the United States or its allies.

The "Doctrine for Joint Nuclear Operations," which was last updated 10 years ago, makes clear that "the decision to employ nuclear weapons at any level requires explicit orders from the president."

But it says that in a changing environment "terrorists or regional states armed with WMD will likely test U.S. security commitments to its allies and friends."

"In response, the U.S. needs a range of capabilities to assure friend and foe alike of its resolve," says the 69-page document dated March 15.

A Pentagon spokesman said Saturday evening that Navy Cmdr. Dawn Cutler, a public affairs officer for the chairman of the Joint Chiefs of Staff, has issued a statement saying the draft is still being circulated among the various services, field commanders, Pentagon lawyers and Defense Secretary Donald H. Rumsfeld's office, .

Its existence was initially reported by The Washington Post in Sunday editions, which said the document was posted on a Pentagon Internet site and pointed out to it by a consultant for the Natural Resorces Defense Council.

The file was not available at that site Saturday evening, but a copy was available at http://www.globalsecurity.org.

"A broader array of capability is needed to dissuade states from undertaking ... courses of action that would threaten U.S. and allied security," the draft says. "U.S. forces must pose a credible deterrent to potential adversaries who have access to modern military technology, including WMD and the means to deliver them."

It says "deterrence of potential adversary WMD use requires the potential adversary leadership to believe the United States has both the ability and will to pre-empt or retaliate promptly with responses that are credible and effective."

It says "this will be particularly difficult with nonstate (non-government) actors who employ or attempt to gain use of WMD. Here, deterrence may be directed at states that support their efforts as well as the terrorist organization itself.

"However, the continuing proliferation of WMD along with the means to deliver them increases the probability that someday a state/nonstate actor nation/terrorist may, through miscaluation or by deliberate choice, use those weapons. In such cases, deterrence, even based on the threat of massive destruction, may fail and the United States must be prepared to use nuclear weapons if necessary."

It notes that U.S. policy has always been purposely vague with regard to when the United States would use nuclear weapons and that it has never vowed not to be the first to use them in a conflict.

One scenario for a possible nuclear pre-emptive strike in the draft would be in the case of an "imminent attack from adversary biological weapons that only effects from nuclear weapons can safely destroy."

The Bush administration is continuing to push for development of an earth-penetrating nuclear warhead, but has yet to obtain congressional approval.

However, the Senate voted in July to revive the "bunker-buster" program that Congress last year decided to kill.

Administration officials have maintained that the U.S. needs to try to develop a nuclear warhead that would be capable of destroying deeply buried targets including bunkers tunneled into solid rock.

But opponents said that its benefits are questionable and that such a warhead would cause extensive radiation fallout above ground killing thousands of people. And they say it may make it easier for a future president to decide to use the nuclear option instead of a conventional weapon.

The Senate voted 53-43 to include $4 million for research into the feasibility of a bunker-buster nuclear warhead. Earlier this year, the House refused to provide the money, so a final decision will have to be worked out between the two chambers.